M2M (Machine-To-Machine) for transmitting and receiving data between machines (including a server) via a network and for autonomously performing an enhanced control or operations is currently being standardized. Moreover, with a huge data group called big data, it is expected, for example, to achieve findings useful for business or a society, and to implement a new mechanism or a system. Thus, the demand for collecting, via a network, data measured or obtained by various sensors present in fields such as a power meter, a gas meter, an electric sensor (a television, an air conditioner, or the like), a surveillance camera, a working machine, a vending machine, and the like has been increasing.
FIG. 1 is an explanatory diagram of a conventional data transfer method. The conventional data transfer method illustrated in FIG. 1 is an example of a case where a plurality of buildings 1 (1-0 to 1-n) are assumed to be a field and data measured or obtained by sensors 15 present in the field are collected. Two data centers (DCs) 3 (3-0, 3-1) are used to collect data. Actual data collection and storage are performed by servers 31 installed within the data centers 3.
In the servers 31, a service application program (SA. Hereinafter abbreviated to “service app”) for executing a process such as an analysis or the like of the collected data is executed. SA1 to SA3 illustrated in FIG. 1 respectively represent service apps of different types. Actual data collection and saving are performed by the buildings 31 installed within the data centers 3. The three servers 31-0 to 31-2 that execute different service apps basically collect only target data.
In each of the buildings 1, a gateway (GW) 11 for relaying data inside and outside the local building 1 is installed, and a GW 16 is installed also on each floor 10. A WAN (Wide Area Network) 2 is built between each of the buildings 1 and each of the DCs 3. In the WAN 2, a plurality of GWs 21 having a different responsible area are placed. FIG. 1 illustrates only two GWs such as a GW 21-0 responsible for an area A, and a GW 21-1 responsible for an area B.
Also in each of the DCs 3, one or more GWs 32 for externally relaying data are installed. FIG. 1 illustrates two GWs 32-0 and 32-1 in the DC 3-0, and one GW 32-2 in the DC 3-1.
In the above described system configuration, data transmitted from the sensor 15 present within each of the buildings 1 is transferred to the server 31 via a transfer path from the GW 16 with which the sensor 15 can communicate, to the GW 11, to one or more GWs 21 in the WAN 2, and to the GW 32 within the DC 3. In FIG. 1, a transfer destination of the data transmitted from the sensor 15 is the server 31-0. Numbers 1 to 4 used in “GW1” to “GW4” illustrated in FIG. 1 represent an order where data is transferred among the GW 16, the GW 11-n, the GW 21-1, and the WAN 32-0 when the data is transmitted from the sensor 15 present in the building 1-n. 
The above described data transfer is implemented in a way such that the GWs 16, 11, 21, and 32 respectively reference transfer tables 16A, 11A, 21A, and 32A. The transfer tables 16A, 11A, 21A, and 32A are tables for storing a type of data, and an address (transfer destination address) of a transfer destination of the data for each entry (record). Contents of each entry are set by the GW controller 4. The transfer destination having a transfer destination address is a GW or a server 31. Data of “power” depicted as an example of the type of data is data that represents power consumption measured by an electric sensor, or a sensor such as a power strip, or the like.
Each of the sensors 15 stores identification information that indicates a type of data in a body of a message in addition to the data to be transmitted so that the data can be transferred by referencing the transfer tables 16A, 11A, 21A, and 32A (FIG. 5). A GW that receives the message identifies the type of the data by referencing the body of the received message, and transfers the message to a transfer destination specified by the transfer table. As a result, each of the buildings 31 can collect data of a target type.
The sensors 15 are not limited those fixed within a field. Many sensors 15 are movable. For example, a power strip that can measure power consumption can be easily moved. Accordingly, it is preferable to assume a move of the sensors 15.
With the move of the sensors 15, a transfer path of data sometimes varies. For example, when the sensor 15 moves from the building 1-0 to the building 1-n as illustrated in FIG. 1, data transmitted from the sensor 15 is received by the GW 16 that is installed on a floor 10 of the building 1-n. In this case, the data transmitted from the sensor 15 cannot be transferred to the server 31-0 if an entry corresponding to the sensor 15 is not present in the transfer table 16A of the GW 16. This transfer cannot be performed if the entry corresponding to the sensor 15 is not present in the transfer tables 11A and 21A respectively referenced by the GW 11-n and the GW 21-1.
A transfer path is decided according to the position of the sensor 15 and the type of data transmitted by the sensor 15. The transfer table of each GW is set according to a decision result of the transfer path. Accordingly, when the sensor 15 is moved to a position at which a communication is performed with a GW that does not have an entry needed in the transfer table, it is general to change a setting for adding an entry also to transfer tables of GWs other than the GW. In the example illustrated in FIG. 1, it is needed to change settings of the transfer tables of the GW 16, the GW 11-n, and the GW 21-1 in the building 1-n when the sensor 15 is moved from the building 1-0 to the building 1-n. Therefore, if times t1 to t3 are respectively needed to change the settings of the transfer tables of the GW 16, the GW 11-n, and the GW 21-1, the length of time needed to change the settings of all the transfer tables results in t1+t2+t3 or longer. A GW for which the setting of the transfer table needs to be changed is identified according to a move destination of the sensor 15. Accordingly, it is difficult to quickly cope with a move of the sensor 15 to a site at which data transmitted by the sensor 15 cannot be suitably transferred. To collect a lot more data from the sensors 15, it is also important to enable a faster change of the setting of a transfer destination of data to GWs positioned from the sensors 15 to an information management server (service app) in the DC, which desires to collect data, when the sensor 15 moves within the building.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2000-138711